The present invention relates to an engine controller for controlling an engine mounted in a vehicle.
Patent Document 1 discloses prohibiting, under a certain condition, occurrence of switching from an EV (electric vehicle) mode in which the vehicle travels by use of a motor to a hybrid traveling mode in which the vehicle travels by activation of an engine.
Specifically, a technique disclosed in connection with Patent Document 1 aims at improving fuel consumption by controlling driving of the engine.
An engine catalyst has heretofore been known as remaining inactive in a cold state and exhibits degradation in capability of purifying an automobile gas emission. Accordingly, if an attempt is made to increase an engine output in a state where the engine catalyst remains inactive, contents of hazardous substances in the automobile gas emission may increase.
In a hybrid car, even when a necessity to start the engine has arisen, a necessary output can be acquired for a short period of time so that the motor is driven by electric power fed from a battery. For this reason, when the engine is started in a circumstance where the engine catalyst is at a low temperature, a catalyst warm-up mode is set within a predetermined warm-up period. In the catalyst warm-up mode, an output value of the engine is set to a predetermined limit value in spite of a required output value of the engine. The limit value is set so that standards for automobile gas emission regulations can be fulfilled even when the engine catalyst remains in active.
If the warm-up period is too long, the battery may be excessively consumed. For this reason, the warm-up period is generally determined to such an extent that the engine catalyst can be made active to a minimum required extent. For this reason, there is no guarantee that the engine catalyst is sufficiently made active in the catalyst warm-up mode.
When the necessity of driving the engine in the warm-up period becomes obviated, the engine is stopped concurrently with the end of the warm-up period, a shift to the EV mode takes place. When another necessity of starting the engine additionally arises, a shift to the hybrid traveling mode newly takes place. If the engine catalyst is made active to a certain extent, the catalyst warm-up mode will not be set. Accordingly, despite a state in which the engine catalyst is not sufficiently made active, the engine output can be increased such that a required output is obtained. In such a circumstance, there could be an increase in contents of hazardous substances in the automobile gas emission.
By way of example, as illustrated in FIG. 8, in a period P11 during which an SOC (state of charge) is a threshold value THsoc or more; during which a vehicle request output becomes low; and during which a vehicle speed comes to a threshold value THspeed1 or less, the vehicle shifts to the EV mode in which the engine is stopped regardless of the vehicle speed. In this case; however, when the vehicle request output becomes high or when the vehicle speed comes to the threshold value THspeed1 or more, the engine is started even when the SOC is the threshold value THsoc or more.
At time point T11, the vehicle speed is threshold value THspeed2 or more, and the SOC is less than the threshold value THsoc. Therefore, the engine is started. However, the catalyst warm-up mode is set in a warm-up period P12 at the beginning of engine starting, whereupon the output value of the engine is limited to a limit value.
Although the vehicle speed becomes less than the threshold value THspeed2 at time point T12, the engine is not stopped in the warm-up period P12.
The warm-up period P12 ends at time point T13, and the vehicle speed is less than the threshold value THspeed2, so that the engine is stopped.
The SOC is still less than the threshold value THsoc at time point T14, and the engine is re-started in response to the vehicle speed's increase in excess of the threshold value THspeed2. Subsequently, the output value of the engine is controlled so that the required output value is obtained.
In such a case, the engine operates in only the warm-up period P12, the engine catalyst might not be sufficiently made active. When the engine is re-started at time T14, the contents of the hazardous substances in the automobile gas emission could increase when the engine is re-started at time point T14.
As is clear from the above descriptions, when an operation period of the engine concomitant with initial starting of the engine has become only the warm-up period, the engine catalyst may be insufficiently made active, and the contents of hazardous substances in the automobile gas emission might increase when the engine is re-started
[Patent Document 1] JP-A-2009-29386